[PSUBS-MAILIST] Dive report: Snoopy at Seneca

Mon Jun 8 17:26:42 EDT 2015

Actually Brian's idea is picking up steam in my mind!  The power loss your experiencing would not happen if the motor is open to the water because the motor is truly equal on both sides.    

Hank--------------------------------------------
On Mon, 6/8/15, hank pronk via Personal_Submersibles <personal_submersibles at psubs.org> wrote:

 Subject: Re: [PSUBS-MAILIST] Dive report: Snoopy at Seneca
 To: "Personal Submersibles General Discussion" <personal_submersibles at psubs.org>
 Received: Monday, June 8, 2015, 5:16 PM

 Alec,
 I have the same problem with my drive on Gamma,
 when returning to the surface the shaft tube is under
 pressure.  I have a ball valve mounted to the tube and even
 a month later there is pressure until I open the ball
 valve.  I have tried a softer compensation bladder with no
 luck.  There has to be an air pocket that we are not
 getting rid of.  Brian's suggestion is not bad at all,
 forget the bladder and rig an open hose with traps so the
 oil can not escape.  There would be an air space trapped
 between the oil and water in the length of tube.  That air
 bubble would simply move in two directions depending on
 depth.  A very simple solution, more tricky for you because
 your motors rotate.  I think I will test this idea since I
 have my tail assembly off for repairs anyways.
 Hank--------------------------------------------
 On Mon, 6/8/15, Alec Smyth via
 Personal_Submersibles <personal_submersibles at psubs.org>
 wrote:

  Subject: Re:
 [PSUBS-MAILIST] Dive report: Snoopy at Seneca
  To: "Personal Submersibles General
 Discussion" <personal_submersibles at psubs.org>
  Received: Monday, June 8, 2015, 4:48 PM

  OK, let me

 try to reason this through again. Lets say the standard
  trolling motor shaft seal is watertight to 50
 feet, and that
  initially I had 1 cubic inch
 of bubble in the system. Dive
  to 250 feet
 and what I would have thought would happen is
  that the 1 cubic inch of air would be reduced
 to 1/8th in3
  due to 8 atmospheres of
 pressure increase. I would have
  expected
 that the compensation bladder would have just been
  squeezed by that volume, and that upon
 surfacing the bubble
  would go back to 1 in3
 and the pressure in the motor to 1
  atm.
 However, what we found was that the motor upon
  surfacing was significantly pressurized. The
 compensation
  bladder (i.e. hose) was
 visibly distended by internal
  pressure upon
 surfacing. There was no leak at the hose

 clamps, but oil was leaking from the shaft seal.
  Since there was over-pressure

 surfaced, clearly water had to have entered the system
  during the dive, and as the hose clamps were
 leak free and
  the seal was not, I suspect
 the seal. Now the question is
  why water
 would get in. Bubble greater than the compression
  range of the hose? Seal offering less
 resistance than the
  hose to compression?
 Shaft pumping water under the seal
  during
 operation due to abrasions? Thermal contraction?
  I'm actually not sure - any theories are
 welcome. One
  interesting detail - the stern
 thruster, which was not
  working due to the
 issue with the speed controller, did not

 have any oil leaks. Both side thrusters, operating,
  did.
  The side
  thrusters being feeble can be explained by
 pressure on their
  seals, or just by their
 age and related wear on the
  commutators. I
 will be changing them, or at least their

 internals.

  Best,
  Alec 
  On Mon, Jun 8, 2015 at
 2:54
  PM, Jon Wallace via
 Personal_Submersibles <personal_submersibles at psubs.org>
  wrote:

    It sounds like at some point water pressure at
 the
  seal was able

    to compress the bubble of air in the tube,
 the
  opposite of what

    was expected.

        I'm kind of stumped by
 the description of the
  motors
 performance
        being
 "feeble" however.  This couldn't
  have been primarily due to

      pressure I don't think.  Also,
 isn't an easy
  fix just to
 "clamp"
        the
 tube any place where liquid appears assuming the
  tube is held

    in a vertical position and the bubble is at
 the top
  (ie vise grip

    the tube).

        Jon

        On 6/8/2015 12:01 PM, Brian
 Cox via
  Personal_Submersibles wrote:

          Hmm,
 guess I'm not getting what is

 happening

          Brian

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